1. Field of the Invention
The invention relates generally to a binary feed mechanism and more particularly to a binary feed mechanism which may be utilized in a programably controlled tube bending machine to control the longitudinal positioning of a plurality of bends along the length of a tube, the radial orientation of the bends, and the depth thereof.
While the binary feed mechanism of the present invention was developed specifically for a tube bending machine for forming automobile exhaust pipes from straight stock, it can be used to control any type of feed movement and should not, therefore, be limited to the tube bendng applications described herein.
2. Description of the Prior Art
One particular application of the present invention is in automated tube bending machines for forming tailpipes for automotive use. Automobile tailpipes or exhaust pipes come in all sizes and shapes. This is due to the fact that first the automobiles are designed and then the exhaust pipes must be designed to fit the existing automobiles. The exhaust pipes or tailpipes are generally made by bending a length of tubing of an appropriate diameter at several selected spaced locations along its length. Each of the bends in the tubing has a predetermined radial orientation with respect to each of the other bends along the longitudinal axis of the tube and each has a predetermined angle or depth of bend.
The tubes used to make articles such as tailpipes for automobiles and furniture frames and the like which consist primarily of bent metal tubing originally employed making a first bend in one machine and then manually removing the tube to another machine where a second bend was made, and continuing in this manner until the article was completely shaped. In such applications, labor was quite expensive and greatly added to the product cost.
Subsequent innovations enabled a single machine to be used for forming a series of bends in a metal tubing or rod which is controlled so as to perform a sequence of bends of various configurations and orientations along the length of the part. The information necessary for the performance of such bends is often introduced in a coded matter prior to the initiation of first operation. The information normally relates to (1) the position of the bend along the length of the pipe; (2) the polar position of the bend with respect to the previously formed bends; and (3) the depth of the bend.
These early automated machines often required a skilled craftsman to operate the machine since several of the parameters still had to be set manually by adjusting various limit stops or the like. Some systems required the longitudinal positioning to be done manually while others required the radial orientation of the tube to be set manually by rotating an indexing disc attached to the workpiece. Eventually, however, nearly fully automated machines were designed which controlled the above parameters without human intervention.
Generally, these fully automated systems are quite expensive, relatively complex and difficult to maintain. Nearly all of these systems require some type of sensing device or transducer which continually monitors the actual longitudinal position of the tube, its angular orientation, and the depth of the bend and feeds back this information to a control system. The control system compares the feedback information with programed information representative of the desired longitudinal positioning, angular orientation, or depth, and terminates the operation when the values are alike. These systems require complex electrical feedback circuitry, motion transducers, and comparators, all of which add to the cost and complexity of the system. Still other systems use digital feedback techniques and employ counters and digital comparators determining when proper positioning has occurred. Still others employ analog techniques to compare the feedback signal with a signal indicative of the desired feed to generate an error voltage which operates a servo motor to make the necessary corrections These systems are prone to failure, difficult to mainain, costly, and do not appear to have gained broad commerical acceptance in the art.
The present invention solves all of these problems by providing a relatively simple, low-cost binary feed mechanism which provides a programably-controlled positive increment of feed without the use of feedback techniques.
The prior art United States Patents listed below are cited as being typical of the programably-controlled tube bending machines of the prior art.
U.S. Pat. No. 3,075,568--F. E. Bright
U.S. Pat. No. 3,426,562--F. Inda
U.S. Pat. No. 3,156,287--H. Munro
U.S. Pat. No. 3,557,586--D. A. Zmuda
U.S. Pat. No. 3,181,323--K. Bos
U.S. Pat. No. 3,650,140--D. A. Zmuda
U.S. Pat. No. 3,299,681--C. F. Hautau
U.S. Pat. No. 3,772,905--C. V. Peddinghaus
U.S. Pat. No. 3,808,856--B. J. Lance
U.S. Pat. No. 3,387,473--H. Noordhoek et al